JEE MainChemistryGeneral Organic Chemistry
The correct decreasing order of stability of the following carbanions is: (I) Cyclopentadienyl anion (II) p -Nitrobenzyl anion (III) Benzyl anion (IV) Cyclopropenyl anion
Options
- A(I) > (III) > (II) > (IV)
- B(IV) > (II) > (III) > (I)
- C(II) > (III) > (I) > (IV)
- D(I) > (II) > (III) > (IV)
Correct answer
D. (I) > (II) > (III) > (IV)
Step-by-step solution
The stability of carbanions depends on factors like aromaticity, resonance, and inductive/mesomeric effects. (I) Cyclopentadienyl anion is a planar, cyclic system with 6 electrons. It follows Huckel's rule and is aromatic, making it exceptionally stable. (IV) Cyclopropenyl anion is a planar, cyclic system with 4 electrons. It is anti-aromatic and highly unstable. (II) p -Nitrobenzyl anion and (III) Benzyl anion are both stabilized by resonance. However, in the p -nitrobenzyl anion, the - NO ₂ group exerts strong -